Air compressing apparatus



Dec. 4, 1956 COTTER 2,772,830

AIR COMPRESSING, APPARATUS Filed June 22, 1953 2 Sheets-Sheet Il 10o 5 178 g 179 1'50 i i8i Z 4.02

160 46 INVENTOR. 14 George L. Cotter '7 i f g awmzm an 20115 n? 66 65 ATTORNEY 4, 1956 G. L. coTTER 2,772,830

AIR COMPRESSING APPARATUS Filed-June 22, 1953 2 Sheets-Sheet 2 212 2 1 III 6 152 is 152 2 47 i i 452 l56 152155 81 5o i41\2 7 145 155 51 i48 7 I INVENTOR.

George-L. Cotter BY duwmm A T TOENE Y AIR COMPRESSING APPARATUS George L. Cotter, Pittsburgh, Pa., assi gnor to Westinghouse Air Brake Company, Wilmerdmg, Pa., :1 corporation of Pennsylvania This invention relates to air compressors and more particularly to means for controlling the operating temperatures thereof. 7

In my copending application, Serial No. 337,141, filed February 16, 1953 and assigned to the assignee of the present application, there is disclosed mechanically controlled apparatus for effecting admittance of a quantity of cooled compressed air into a compressor cylinder, during each successive compression stroke of the compressor piston, in order to raise the pressure of the initial charge of atmospheric air in said cylinder independently of the compressive action of the piston movement and consequently without the corresponding generation of heat, thereby reducing the amount of work performed by said piston in raising the pressure in the cylinder from atmospheric pressure to discharge pressure and thus reducing the heat of compression generated per stroke below that which would prevail without admission of the cooled compressed air.

It is a prime object of the present invention to provide a fiuid-pressure-controlled apparatus for controlling such admittance of the cooled compressed air into the compressor cylinder during each compression stroke of the compressor piston to serve the same purpose as set forth above.

Other objects and advantages will become apparent from the following more detailed description of the invention taken in connection with the accompanying drawings in which:

Fig. 1 is an elevation'view, partly in outline and partly insection, of a fluid-pressure-controlled, cooling air admittance control apparatus embodying the invention, shown in association with a compressed air supply system;

Figs. 2, 3, and 6 are views, similar to Fig. 1, of different embodiments of the invention which afford various operational features as set forth in detail hereinafter; and

Fig. 4 is an elevation view, partly in outline and partly in section, of a magnet valve device employed in the apparatus shown in Figs. 3, 5 and 6.

Description Referring to the drawings, the air compressing system with which the cooling air admittance control apparatus is associated comprises an air compressor 1, a storage reservoir 2, and aftercooler coils 3.

For the purpose of illustration, the air compressor 1 comprises a cylinder casing 4 having the usual piston 5 reciprocable therein in sliding sealing engagement with the usual inner cylinder wall 6 formed in said casing. I In the well-known manner, the piston 5 serves as a movable abutment defining one end of the usual cylinder chamber 7, the opposite end of which chamber 7 is closed by a pressure head 8 containing the usual inlet and discharge valves 9 and 10, respectively, which control admission of free air to and discharge of compressed air from the cylinfor cooperation with a valve seat 11 to control commu- United States Patent 0 0 2,772,830 Patented Dec. 4, 1956 "ice nication between an inlet port 12 in pressure head 8 and the cylinder chamber 7 via an inlet chamber 13, constantly connected to port 12 and a bore 14 in which a fluted stem 14a attached to inlet valve 9 is slidably guided; and exhaust valve 10 being disposed in a discharge chamber 15 and arranged for cooperation with a valve seat 16 to con trol communication between a discharge port 17 and the cylinder chamber 7 by way of the chamber 15 and a port 18. A light compression spring 19, disposed in the inlet chamber 13 is arranged to cooperate with the fluted stern 14a to bias the inlet valve 9 toward its seated position, in which it is shown in the drawing, closing off the cylinder chamber '7 from the inlet port 12, and a similar light compression spring 20,'disposed in discharge chamber 15, is arranged to bias the dischargevalve 10 toward its seated position, in which it is shown in the drawing, closing off the cylinder chamber 7 from the discharge port 17.

In the well-known manner, movement of piston 5 through its suction stroke from top dead center position in proximity of the pressure head 8 to bottom dead center position in which it is shown on the drawing, will cause a suction in cylinder chamber '1 which causes the unseating of inlet'valve 9 and admission of air from the atmosphere into said chamber 7 via inlet port 12, inlet chamber 13, bore 14 and the unseated inletyalve. Subsequent movement of the piston 5 through its compression stroke in the opposite direction, that is, from its bottom dead center position to its top dead center position, will cause compression of the air in chamber 7 and displacement ofsuch air therefrom via port ,18, discharge chamber 15, and port 17 by unseating of the discharge valve 10.

The discharge port 17 is constantly connected to the reservoir 2 via the aftercooler coils 3 which cool'the compressed air discharged from the compressor enroute to the reservoir and it is intended thatthe compressor will operate under suitable controls (not shown) to automatically maintain the air pressure in the reservoir 2 at relatively high discharge pressure in the neighborhood of one hundred pounds per square ,inch, for example, where the operatingftemperature ofsuch compressor tends to become excessive 'due to heat of compression generated during its operation, as otherwise, atmaterially lower discharge pressures where the operating temperatures of the compressor is tolerable, no such cooling means as subsequently set forth herein need be employed. According to the invention, the fluid-pressure-controlled means for affecting admittance of cooled compressed air from thereser'voir 2 into cylinder chamber 7 during each compression stroke of the piston 5, for cooling purposes, comprises a cooling-air-admittance control valve device 30, a choke and check valve device 31 and a pressure relief ty'pe valve device32.

The cooling-air-admittance-control valve device 30 comprises a divided casing 33 having formed therein a cylindrical chamber defined by a cylinder wall 34 which intersects at its opposite ends respective stop elements 35 and,36 formed integral with the casing 33. Disposed within this cylindrical chamber are a pair of piston valves 37 and 38 in slidable sealing engagement with the cylinder wall 34, and spaced apart through the medium of a stem 39 extending therebetween and attached at its opposite ends thereto, respectively. The annular space between the cylinder wall 34, the valves 37 and 38, and encircling the stem 39 defines a cooling air supply chamber 40, while at atmospheric air inlet chamber 41 is defined by the cylinder wall 34, the piston 37, and a partition 42. Ports 43 and 44 are provided in the casing 33 which open inwardly from the exterior thereof into intere section with the cylinder wall 34 in the casing, and said ports are so disposed that port 44 will remain constantly open to the cooling air supply chamber 40 in all positions of the piston valves 37 and 38, while the port 43 will be open to the atmospheric air inlet chamber 41 when the piston valves 37 and 38 are in the positions in which they are shown in the drawing, defined by engagement of the piston valve 38 with the stop element 36, and said port 43 will be open to the cooling air supply chamber 40 when said piston valves are caused to move to a position opposite to that in which they are shown in the drawing and defined by engagement of piston valve 37 with the stop element 35. The port 44 is connected to the reservoir 2 by way of pipes 46, 47 and the device 32, while the port 43 is constantly connected to the inlet chamber 13 in the compressor 1 by way of a pipe 48 and the inlet port 12. The position of the piston valves 37 and 38 in which they are shown in the drawing will hereinafter be referred to as their atmospheric-air-admittance position, in which atmospheric inlet air to the compressor 1 is adapted to be admitted by way of the usual suction strainer 50, a pipe 51, a port 52 in the casing of valve device 30, a spring chamber 53 in said device, ports 54 in the partition 42 of said device, the atmospheric air inlet chamber 41, port 43, pipe 48 and in compressor 1, port 12 and chamber 13. The position of piston valves 37 and 38 opposite to that in which they are shown in the drawing will hereinafter be referred to as their coolingair-admittance position in which the pipe 46 will be opened to the inlet chamber 13 in the compressor 1 by way of the cooling air supply chamber 40 in the device 30, port 43, pipe 48 and the port 12 in said compressor. For actuating the piston valves 37 and 38 from their atmospheric-air-admittance position in which they are shown in the drawing to their cooling-air-admittance position, there is provided a piston 58 reciprocally mounted in a cylindrical chamber formed by such as a bore 59 in the casing 33. The bore 59 is formed in coaxial alignment with the cylinder wall 34 at one side of the stop element 36 which defines an end wall of a spring chamber 60 within said bore at one side of the piston 58. The opposite end of the bore 59 is closed by the usual end cap 61 which defines an end wall of a pressure control chamber 62 between the wall of said bore and the piston 58. A piston rod 63 is attached at its one end to the piston 58 and at its opposite end to the piston valve 38, a central opening 64 in the element 36 serving to accommodate the stem 63 which extends with clearance therethrough. A compression spring 65 is disposed in spring chamber 60 in encirclement of the piston rod 63, and in abutment at its one end with the stop element 36 and at its opposite end with the piston 58 to urge piston 58 in the direction of pressure chamber 62 to a repose position in which it is shown in the drawing and defined by engagement of the piston valve 38 with the said element 36. The pressure chamber 62 is constantly open to the cylinder chamber 7 in the compressor 1 by way of a port 66 in the casing 33 of the device 30, a pipe 67 and a port 68in the pressure head 8 of the compressor 1 which opens into said cylinder chamber 7 adjacent the inlet valve 9.

During each successive compression stroke of the piston in compressor 1, when the pressure of fluid in cylinder chamber 7, and as realized in pressure chamber 62 in the device 30, attains a value such as two or three pounds per square inch, for example, such pressure will cause movement of the piston 58 from its repose position, in which it is shown in the drawing, against opposition of the control spring 65 and in the direction of spring chamber 60 to cause movement of the piston valves 37 and 38 in the direction of chamber 41 to the cooling-airadmittance position, previously defined, thus establishing, during each successive compression stroke of the piston 5, the communication between the inlet chamber 13 in the compressor 1 and the main reservoir 2 by Way of the pipe 47, pressure relief valve 32, the pipe 46, and in device 30, port 44, cooling air supply chamber 40 and port 43, the pipe 48, and the port 12 in the compressor. 1; thereby to permit admittance of the cooled compressed air, at such as one hundred pounds per square inch, from the reservoir 2 I atmospheric-air-admittance position, in which they are shown on the drawing, there is provided in the device 30 a piston 70 reciprocably mounted within a cylindrical chamber formed by a bore 71 in the casing 33. The p1ston 70 is subject opposingly to pressure of fluid in a pressure chamber 72 at one side and the force of a compression spring 73 disposed in non-pressure or atmospheric chamber 53 at its opposite side. The compression spring 73 is interposed between the partit on 42 and the piston 70 and urges said piston in the direction of the pressure chamber 72 to a repose position defined .by engagement of said piston with a stop element 76. A piston valve actuating stem '77 is attached at one end centrally to the piston 70 and extends through the chamber 53 and through a central opening in the partition 42 for projection into the atmospheric air inlet chamber 41 in encirclement by the stop element 35. The length of the 'piston valve actuating stem 77 is such, relative to location of the stop element 35, that in repose position of the piston 70, said rod will not interfere with movement of piston valve 37 into engagement with said stop element 35.

The pressure chamber 72 in the device 30 is in constant communication with the cylinder chamber 7 in the compressor 1 by way of a port 80 in the casing 33 of device 30, a pipe 81, the choke and check valve device 31, the pipe 67, and the port 68 in the compressor 1.

The choke and check valve device 31 comprises the usual check valve 81a and choke 82 which are arranged to allow for relatively unrestricted flow of compressed air from the pipe 67 to the pressure chamber 72 in the device 30 via pipe 81, and restricted flow by way of the choke 82 in the opposite direction, that is, from said chamber 72 to said pipe 67.

Prior to operation of piston 70 from its repose position, and while the piston valves 37 and 38 are caused to move from their atmospheric-air=admittance position, in which they are shown in the drawing, to their coolingair-admittance position by operation of the piston 58 in response to pressurization of the chamber 62, the spring 73 acting on piston 70, being of a higher value than that of the spring acting on piston 58, will maintain the piston and stem 77 in the repose position, in which they are shown in the drawing, while pressure of fluid in the chamber 72 increases with that in the chamber 62, by way of the pipe 67, check valve 81a, pipe 81 and port 80.

During a later stage of each successive compression stroke of the compressor pisotn 5, subsequentto operation of the piston 58 in device 30 to cause piston valves 37 and 38 to assume the cooling-air-a-dmittance position, previously defined, fluid under pressure from the cylinder chamber 7 supplied to the pipe 67 will flow by Way of the check valve 81a in device 31, the pipe 81, and port 80 in casing 33, into the pressure chamber 72 in the device 30, where the pressure of fluid will thus be increased. When the pressure of fluid in the pressure chamber 72 attains a value, such as seventy pounds per square inch, sufiicient to overcome the action of the spring 73 on the piston 70, such pressure in chamber 72 will cause movement of piston 70 to bring stem 77 into engagement with the piston valve 37 in its cooling-air-admittance position and thereafter, assisted by spring 65, cause said piston valve 37, piston valve 38 and the piston 58, against action of the pressure of fluid in the chamber 62 acting on said piston 58 to be moved to their inlet-air-admitdefined by engagement of the piston valve 38 with the stop element 36. The piston 70 is made suflicieutly larger in diameter than that of the piston 58 so that the same chosen pressure of fluid in chamber 72 as'exists in chamber 62 will be capable of overcoming the action of such pressure in chamber 62 acting on piston 58 as well as the additional opposition presented by spring 73.

With the piston valves 37 and 38 being held in their inlet-air-admittance position which they are caused to assume, as described above, by action of pressure of fluid in chamber 72 on piston 70 created during each successive compression stroke of the compressor piston 5, 'fluid under pressure in chamber 62 in the device 30 will release into cylinder chamber 7 during each following suction stroke of said piston by way of the pipe 67 and the port '68 in the compressor 1, and, at the same time, fluid under pressure in the chamber. 72 in the device 30' will release also into said chamber 7 by way of the pipe 81, choke 82 in the device 31, said pipe 67 and said port 68 in the compressor 1.

When the pressure of fluid in chamber 72 acting on piston 70 is reduced suflicie ntly by such release of fluid under pressure from said'chamber, the spring 73 will cause return of the piston 70 to its repose position in which it is shown in the drawing, and carry the attached stem 77 to its corresponding repose position disposed away from the piston valve 37.

At the time that the piston 70 and the stem 77 are thus returned to their respective repose positions, dis posed away from the piston valve 37, said piston valve 37 and attached piston valve 38 and piston 58 will remain, under the action of spring 65, in the atmosphericair-admittance position, in which they are shown in the drawing, due to the pressure of fluid in chamber 62 having been depleted in advance of that in chamber 72 by virtue of the restrictive action of the choke 82 on release of fluid from said chamber 72.

From the foregoing, it will be appreciated that during each successive inlet stroke of the compressor piston 5, atmospheric air will be admitted into the cylinder chamber 7 of compressor 1 by way of the suction strainer 50, pipe 51, the port 52, chamber 53, the ports 54 in partition 42, the atmospheric air inlet chamber 41, past the piston valve 37 in its :atmospheric-air-admittance position, the port 43, the pipe 48, the port 12, the inlet chamber 13, the bore 14, and the inlet Valve 9 unseated by the suction action of movement of the piston as set forth hereinbefore; and, during the early stage of each successive compression stroke, cooled compressed air from the reservoir 2 at a higher pressure than that existing in cylinder chamber 7 in compressor 1 will be admitted to said cylinder chamber 7 by way of the pipe 47, the pressure relief valve device 32, the pipe 46, the port 44, the cooling air supply chamber 40 between the piston valves 37 and 38 in their uppermostc ooling-airadmittance position, port 43, the pipe48, the port 12, inlet chamber 13, bore 14, and the inlet valve 9 unseated by virtue of preponderance in pressure of such cooled compressed air over that pressure existent in the cylinder chamber 7 during movement of the piston 5 through its respective compression stroke.

During a subsequent stage of each successive compression stroke of the compressor piston 5, movement of the piston valves 37 and 38 from their cooling-'air adtnittance position to their atmosphe ric-air-admittance position will interrupt communication between the pipe 48 and the 30 and the suction strainer 50 as set forth above, pressure of fluid in the inlet chamber 13 in the compressor 1 will reduce sutficiently by virtue of release of compressed air therefrom by way of port 12, the pipe 48 and device 30 to permit spring 19 to close the inlet valve 9 for the subsequent duration of each successive compression stroke, at the completion of which, the air compressed in the cylinder chamber 7 will discharge to the reservoir 2 by way of the discharge valve 10, discharge chamber 15, and the aftercooler coils 3 in the well-known manner, as set forth hereinbefore.

The action of the pressure release valve device 32 is such that its piston valve will remain closed at reservoir pressures below some such value as forty pounds, so that even though the control device 30 may operate to call for admittance of cooled compressed air to the compressor 1 at reservoir pressures below the setting of device 32, such admittance will be prevented. When the pressure of fluid is above forty pounds, chosen for example, the piston valve 90 in the device 32 will unseat against action of the spring 91 to open the chamber 92 connected to the pipe 47 to the pipe 46 and thereby to the cooling air supply chamber 40 in the device 30, whereupon, continued operation of the device 30 when reservoir pressure is above forty pounds will effect admittance of cooled compressed air to the cylinder chamber 7 in the compressor 1 in the same manner as described hereinbefore.

According to an optional feature of the invention as shown in Fig. 2, means are provided for establishing communication selectively between the pressure chamber 62 in the control device 30 and either the cylinder chamber 7 in the compressor 1 or the reservoir 2, according to pressure of fluid in the reservoir, to cause the control device 30 to operate either in the manner as aforedescribed for admitting cooled compressed air to the cylinder chamber 7 during operation of the compressor 1 when there is a demand for fluid under pressure in the reservoir 2,

or, to cause the device 30 to establish communications for constant circulation of compressed air through the aftercooler 3, the reservoir 2 and compressor 1 during continued operation of the compressor when there is no demand for supply of compressed air to the reservoir, respectively.

Referring to Fig. 2, such means as just mentioned may comprise a pressure responsive valve device and a shuttle valve device 101. For sake of illustration, schematically, the pressure responsive device 108 may comprise a hollow casing 102 having a piston valve N93 slidably mounted therein subject to pressure of fluid in a pressure chamber 104 at one side and to the force of the compression spring 195 in an atmospheric chamber 106 at its opposite side. The pressure chamber 1G4 is constantly open to reservoir 2 by way of a branch of the pipe 47. The compression spring 105 disposed in chamber 106 is arranged to urge the piston valve 103 in the direction of chamber 104 to one position defined by engagement of said piston valve 163 with an annular seat 107 encircling the opening of the pressure chamber 104 with the respective branch of the pipe 47.' The piston valve 193 is provided with a passage 198 which in its said one position establishes communication between an atmospheric port 199 and one inlet opening of the shuttle valve device 101 via a pipe 113. With the piston valve 163 in the position in which it is shown in the drawing establishing communication between the one inlet 110 ofthe shuttle valve device 101 and the atmospheric port 1%9, when pressure of reservoir fluid, as real-' ized in the pressure chamber 104 within theconfines of the annular seat 107, increases suiiiciently to overcome action of the spring 105 such as 100 pounds per square inch, for example, said piston valve will move in the direction of chamber 106 to a second position defined by engagement of' said piston valve with an annular stop shoulder 111 in which is established communication between another branch of the reservoir pipe 47, and the passage 108 in said piston valve 103 by way of a port 112 in the casing of device 100 to allow for flow of fluid under pressure from the reservoir 2 to the said one inlet 110 of the shuttle valve device 101 by way of said other branch of the pipe 47, the passage 108 in piston valve device 100, and pipe 113.

Prior to the unseating of the piston valve 103 from the annular seat 107, the inner circular portion of said piston valve, definedby contact of the rib of the annular seat 107 with said piston valve, will be exposed to pressure of fluid in said chamber 104, but immediately upon unseating of said piston valve 103 from said annular seat 107 the entire surface of said piston 'valve will become exposed to the pressure of fluid in said chamber 104 and said valve will move from its one position, in which it is shown in the drawing, to its opposite position, in engagement with the annular stop shoulder 111, with a rapid or snap action. Upon subsequent reduction in pressure of fluid in the pressure chamber 104 to some such value as 70 pounds, for example, the compression spring 105 will effect return of the piston valve 103 from its position in engagement with the annular stop shoulder 111 to its position in which it is shown in the drawing in engagement with the annular seat 107.

The shuttle valve device 101, for sake of illustration, may simply comprise the usual casing 115 having the usual shuttle valve 116 slidably mounted therein to selectively establish communication between either the previously mentioned inlet 110 and an outlet 117 or between said outlet 117 and a second inlet 118, according to preponderance in pressure of fluid in one or the other of the said two inlets;

In addition, in order to render the reservoir pressure A of fluid admitted to chamber 62 effective to maintain the piston valves 37 and 38 disposed in their cooling-airadmittance position in accord with the feature in discussion, means are provided in the form of a magnet valve device 400, a pressure switch device 401, and a source of electric current such as a battery 402, arranged to selectively establish communication of the chamber 72 in device 30 to either the atmosphere or to the chamber 7 in the compressor 1 according to whether or not the pressure chamber 62 in the device 30 is or is not pressurized with reservoir fluid.

Referring to Fig. 4, for sake of illustration, the magnet valve device 400 may simply comprise a casing 135 having three chambers 136, 137, 138, separated one from the other by means of the usual partitions 139, 140 and provided with the usual valves 141, 142 to establish selective communication between chamber 137 and chambers 136, 138. A compression spring 143 disposed in chamber 138 is arranged in cooperation with the valve 142 to urge same to a seated position, in which it is shown in the drawing, closing oil. the chamber 137 from said chamber 138 and at the same time, through the medium of fluted stems 145 and 146 causing the valve 141 to be held unseated and thereby establishing communication between the chamber 137 and the chamber 136. Ports 147, 148, and 149 in the casing 135 of the magnet valve device 132 permit communication of the chambers 136, 137, and 138, respectively, with the exterior of said casing for connection with suitable conduits as desired. The usual magnet coil (not shown) energizable by way of terminals 152, 153, are operatively connected to valves 141 and 142 through the medium of a stem 154 to cause actuation of the valves 141 and 142 figures of the drawings by a solid line and a dash line designated by such reference numerals, respectively.

Referring again to Fig. 2, the pressure switch device 401, for sake of illustration, may simply comprise the usual fixed contacts 404 connected in series with battery 402 and with terminals 152, 153 of magnet valve device 400 by way of wires 405, 406. Device 401 may also comprise the usual movable contact 407, operably connected to a piston 409 through the medium of a stern 410, to break and make electrical connection between contacts 404 according to whether or not a pressure chamber 411, to which piston 409 is exposed, is or is not pressurized; pressurization of chamber 411 causing piston 409 to move contact 407 out of engagement with fixed contacts 404, and the usual return spring 412 causing return of piston 409 to the position in which it is shown in the drawing for bridging engagement of contact 407 with said fixed contacts 404 when chamber 411 becomes depressurized.

As previously mentioned, the one inlet, 110, of the shuttle valve device 101 is constantly connected via pipe 113 to the passage 108 in the piston valve 103 of the pressure responsive valve device 100, the opposite inlet 118 of the shuttle valve device 101 is constantly con nected to the choke and check valve device 31 and to the chamber 137 in magnet valve device 400 by way of its port 148, a pipe 311 and branch thereof; and the outlet 117 of the shuttle valve device 101 is in constant communication with the pressure chamber 62 in the device 30 by way of a pipe 119 and port 66. The shuttle valve device 101 may be provided with a light bias spring 120 arranged to maintain the valve 116 in the position in'which it is shown in the drawing when the inlet port 110 is vented to the atmosphere.

In the magnet valve device 400, the chamber 136 is constantly vented to the atmosphere by way of its port 147 and a pipe 310, while the chamber 138 is constantly connected to the cylinder chamber .7 in compressor 1 by way of the port 149, pipe 67 and port 68.

The pressure chamber 411 in pressure switch device 401 is constantly open to the pipe 113, by way of a branch thereof.

According to the particular feature of the invention in discussion, when the pressure of fluid in the reservoir 2 is below a hundred pounds, for a chosen example, and the piston valve 103 in the pressure responsive device is in the position in which it is shown in the drawing establishing connection of its passage 108 with the atmospheric port 109 and with the pipe 113, the inlet port of the shuttle valve device 101 and pressure chamber 411 in pressure switch device 401 will be vented to the atmosphere via pipe 113, as will be appreciated from the preceding description, with contact 407 consequently bridging contacts 404 and the magnet valve device 400 consequently energized. Communication therefore will be maintained between the pressure chamber 62 in the valve device 30 and the cylinder chamber 7 in the compressor 1 by way of the pipe 67, communication 161 in the energized magnet valve device 400, pipe 311, the inlet- 118 and outlet 117 of the shuttle valve device 101, the pipe 119 and the port 66 in the device 30, so that the device 30 will respond during each successive inlet stroke of the compressor piston 5 to allow for admittance of atmospheric air into said chamber 7, and during each successive compression stroke of the compressor piston 5, to effect admittance of a quantity of cooled compressed air from the reservoir 2 into the cylinder chamber 7 for mixture with the atmospheric charge admitted thereto during said suction stroke, in the manner previously described.

When the pressure of fluid in the reservoir 2 attains a value of 100 pounds per square inch, chosen for example, and the piston valve 103 in the pressure responsive valve device 100 assumes its position opposite to that in which it is shown in the drawing and in engagement with the annular shoulder 111 to establish communication between the pipe 47 and the pipe 113, fluid under pressure from the reservoir 2 will flow by way of said pipe 47, passage 108 in piston valve 103, and said pipe 113 into pressure chamber 411 in pressure switch device 401 and into pressure chamber 62 in the control valve device 30 via shuttle valve device 101. Pressurization of chamber 411 in switch device 401 results in opening contact 4117 and deenergization of magnet valve device 400 so that chamber 72 in device 30 Will be maintained v r vented to the atmosphere via pipe 81, choke and check valve device 31, pipe 311, communication 160 in magnet valve device 400, and the pipe 310, so that during the time that the pressure chamber 62 in the valve device 30 is thus pressurized with fluid under pressure from the reservoir 2 by Way of the pressure responsive valve device 100 and the shuttle valve device 101, the piston valves 37 and 38 in the said valve device 30 will be caused to assume and be maintained in their previously defined cooling-air-admittance position by such fluid under pressure in chamber 62 acting on the piston 58, thereby maintaining establishment of communication between the pipe 48 and the cooling air supply pipe 46 by way of the port 43, chamber 40 and port 44 in the device 30. With the pipes 48 and 46 thus in communication one with the other by way of the device 30, during continued operation of the compressor 1, cooled compressed air will be continuously circulated through the system including aftercooler coils 3, reservoir 2, device 30 and compressor 1.

With device 30 thus being maintained in its coolingair-admittance position each successive suction stroke of the compressor piston 5 will cause admittance of compressed air from reservoir 2 to cylinder chamber 7 via the pipe 47, the pressure release valve device 32, the pipe 46; in device 30, port 44, chamber 40, and port 43; the pipe 48; and, in the compressor 1, the port 12, the inlet chamber 13, the bore 14, and the-inlet valve 9.

During each successive compression stroke of the compressor piston 5, such cooled compressed air from the reservoir 2 admitted to the cylinder chamber 7, as just described, will be discharged by the compressor by way of the discharge valve 10, the discharge chamber 15, and theraftercooler coils 3.

The compressed air thus circulated through the system in being recycled through the aftercooler coils 3 with continued running of the compressor without load, effiects additional cooling of such compressed air and therefore of the compressor. During such recirculation of the compressed air through the compressor 1 the inlet valve 9 acts as a check valve to prevent backflow of compressed air from the cylinder chamber 7 to the valve device 30 while the discharge-valve '10s acts as a check valve permitting flow of compressed air from the cylinder chamber 7 to the reservoir 2 by wayfof the aftercooler coils 3 while preventing flow in the reverse direction.

'According to another feature of the embodiment as illustrated in Fig. 2, the pressure of reservoir air, 100 pounds per square inch, chosen for example, may correspond with the usual maximum pressure obtained in the reservoir 2, while the lower pressure value of 70 pounds per square inch, chosen for. example, may correspond with the usual minimum pressure to which it is desirable to allow the pressure offluid in the reservoir to be reduced during use of compressed air from the system, so that when the pressure responsive valve device 10%) responds to such higher pressure in the reservoir 2 to cause the valve device 31) to eifect recirculation of cooled compressed air through system, said compressor 1 operates without appreciable load and is in eifect unloaded, and when the valve device 160 responds to the lower reservoir pressure of 70 pounds to cause the valve device 30 to effect admittance of atmospheric air to the compressor for compression, such admittance in effect loads the compressor. Such system as illustrated in Fig. 2, therefore eliminates the necessity for the usual reservoir-pressure responsive compressor-unloader mechanism associated with the compressor usually employed for holding the inlet valve 9 unseated to eflect unloading.

For this reason the pressure responsive valve device may take the form of the usual pressure goevrnor device employed in compressed airsupply systems for response to the pressure of fluid in the main reservoir to selectively establish communication between the usual unloader control conduit and either the atmosphere or the reservoir.

As illustrated in Fig. 3, according to the feature in immediate discussion, the means for selectively establishing communication between the control chamber 62 in the device 30 and either the cylinder chamber 7 in the compressor 1 or the reservoir 2, as an alternate structure, may comprise a pressure governor switch device'130 in lieu of valve device 100, and a magnet valve device 132 in lieu of the shuttle valve device 101 of Fig. 2. Magnet valve device 132 employed in the apparatus illustrated in Fig. 3 may be similar to magnet valve device 400 of Fig. 2, with its terminals 152, 153 connected in parallel with the corresponding terminals of device 480; device 132 being energizable and deenergizable to establish communication between the pressure chamber 62 in the device 30 and either the reservoir 2 or the cylinder chamber 7 in the compressor 1, respectively.

Referring to Figs. 3 and 4 and to previous description of magnet v'alve device 400, in the apparatus shown in Fig. 3, the chamber 137 in the magnet valve device 132 is in constant communication with the pressure chamber 62 in the valve device 30 via port 148 and pipe 119; the chamber 136 in the magnet valve device 132 is in constant communication with a branch of the supply pipe 47 via of port 147; and the chamber 138 in the magnet valve device 132 is in constant communication with choke and check valve device 31 and the chamber 137 in the magnet valve device 400 by way of port 149 and a branch of the pipe 311. v

Referring to Fig. 3, the pressure governor switch device 130, for sake of schematic illustration, may simply comprise a hollow casing having a piston 17 6 mounted therein subject to pressure of fluid in a pressure chamber 177 at one side and to force of a compression spring 178 disposed in an atmospheric chamber 179 on its opposite side. A switch operating stem 180 is attached to piston 176 at its one end and at its opposite end to an electrical switch element 181 disposed exteriorly of the casing 175 in proper alignment with fixed contacts 170, 172 connected in series with battery 4412 and in parallel with the coils of magnet valve devices 132 and 400. The control spring 178 urges the piston 176 in the direction of the pressure chamber 177 to a switch closed position defined by engagement of said piston with an annular seat encircling a port 191 opening centrally into chamber 177.

The value of the control spring 178 in the pressure switch device 131) is such that, in operation of the apparatus illustrated in Fig. 3, when the pressure of fluid in the reservoir 2, with which pressure chamber 177 in switch device 130 is in constant open communication, attains a value such as 100 pounds per square inch, for example, the piston 176 will move in the direction of chamber 179 and carry contact element 181 out of engagement with electrical contacts 170 and 172, thereby interrupting the energizing circuit through the coils of the magnet valve devices 132 and 400 via the wires 405 and 406 to cause deenergization of said magnet valve devices 132 and 400 for establishing their respective communications 160 for venting of chamber 72 in device 30 (via pipe 81, choke and check valve device 31, pipe 311, communication 160 in magnet valve device 400, and pipe 310) and for admittance of fluid underpressure from the reservoir 2 to the chamber 62 in valve device 30 (via pipe 47, communication" 160 in magnet'valve device 132, and

pipe 119) to position device 30 to cause recirculation of cooled compressed air from the reservoir 2 and the compressor 1 in the manner as previously described in regard to the apparatus illustrated in Fig. 2. Accordingly, when the pressure of fluid in reservoir 2, as realized in the pressure chamber 177 of the pressure switch device 130, drops below the lower limit value of 70 pounds per square inch, chosen for example, the spring 178 in the switch device 130 will cause movement of the piston 176 in said device to return to its repose position, in which it is shown in the drawing, and move the switch element 181 into contact with the switch contacts 170 and 172, thereby establishing the energizing circuit through the magnet coils in the magnet valve devices 132 and 400 to cause same to disestablish their respective communications 160 connecting the pressure chambers 62 and 72 in the device 30 to the reservoir 2 and to atmosphere, respectively, and to establish their respective communications 161 for connecting both of said chambers 62 and 72 in device 30 to the cylinder chamber 7 in the compressor 1 by way of the pipe 311 and pipe 67 for effecting loading of the compressor and admittance of the cooled compressed air thereto during each successive compression stroke of the compressor piston 5 in the manner previously set forth in regard to operation of the device 30 in connection with the apparatus illustrated in Figs. 1 and 2.

According to another optional feature of the invention, illustrated in Fig. 5, means are provided for interlocking operation of the device 30 with speed of operation of the compressor 1.

In certain compressor installations such as in a dieselelectric locomotive, for example, where the compressor is driven by the diesel engine which also drives the generators for propelling the locomotive, the greatest demand for compressed air occurs at a time when the engines and thereby the compressors arc idling and the air brakes on the train driven by the locomotive are in operation, and only rarely is the demand for compressed air excessive when the engine is operating above idling speed during propulsion of the vehicle. Under the circumstances, where the diesel engine driving the compressor is operating at idling speed, there is little or no tendency for the compressor to overheat at such a low speed, but in such rare occasions as where there is such a great demand for air from the compressor 1 at a time when the engine driving the same is operating atrelatively high speeds, it may be desirable to employ such as applicants pressure responsive device 30 for efiecting cooling or admittance of cooling air to the compressor, while at the same time providing means for rendering such device 30 ineffective during operation of the compressor at idling speed.

As shown in Fig. 5, such interlock means may comprise a source of electrical energy such as a battery 131, a magnet valve device 432, and a speed responsive switch dey vice 200.

The magnet valve device 432 may be substantially like that shown in detail in Fig. 4 and as employed in the apparatus shown in Figs. 2 and 3. In device 432, the chamber 136 is connected to the atmosphere by way of port 147 and a pipe 201, the chamber 137 is connected to the chamber 62 in the device 30 by way of port 148 and a pipe 202, and the chamber 138 is connected to the cylinder chamber 7 in the compressor 1' by way of the port 149 and pipe 67. One terminal 152 of the magnet valve device 432 may be connected to one terminal of the battery 131 by way of a wire 203 while the opposite terminal 153 of the magnet valve device 432 may be connected via a wire 220 to one contact 204 of the speed responsive switch device 200, the opposite contact 205 of said speed responsive switch device being connected to the opposite 12 pulsion engine, asabove mentioned) through the medium of such as gears 209 and 210; a fixed shaft 211 on one end of which the rotatable element 200 is journaled; a second sleeve-like element 212 journaled on to said fixed shaft 211 and spaced away from the first rotatable element 207; and a pair of centrifugal flyball Weight elements 213 carried intermediate opposite ends of the usual spring elements 214 attached at their opposite ends to the rotatable sleeve-like elements 207 and 212. The speed responsive switch device 200 also comprises a rotatable contact element 215 attached for rotation with the second sleeve element 212 and suitably arranged relative to contacts 204 and 205 for slidable engagement therewith.

In operation of the speed responsive switch device 200, while the compressor shaft 208 is operating at idling speed or at speeds below idling speed, the element 207 of said device in turning with said shaft will not cause rotation of the centrifugal flyball elements 213 at sufficient speed to cause the contact element 215 to engage the contacts 204 and 205, so that the energizing circuit through the magnet valve device 432 and the battery 131 will be interrupted, but at speeds of the compressor shaft 208 above idling speed, rotation of centrifugal flyball elements 213 will cause said elements to move radially outwardly from the shaft 211, with suflicient flexure of elements 214 to carry sleeve element 212 and attached contact 215 downwardly, as viewed in the drawing, to a position in which the contact element 215 bridges the contacts 204, 205 to complete an energizing circuit through the magnet valve device 432 by way of the wire 206, said contact element, said contacts, the wire 220, the wire 203, and the battery 131.

Thus it will be apparent that the magnet valve device 432 will be deenergized when the compressor 1 is operating at speeds at or below idling speed and will be energized when the compressor 1 is operating at speeds above idling speed.

Referring to Figs. 1, 4 and 5, in operation of the apparatus illustrated in Fig. 5, when the compressor 1 is operating at or below idling speed and the magnet valve device 432 is consequently deenergized, the control chambers 62 and 72 in device 30 are disconnected from the cylinder chamber 7 in the compressor 1 and are connected to the atmosphere by way of communication in magnet valve device 432 and the pipe 201, so that the components of device 30 will remain in their repose positions in which they are shown in Fig. 1, and there will be no admittance of cooled compressed air to the cylinder chamber 7 during continued operation of the compressor at such speeds. 'By virtue of the fact that the cylinder chamber 7 is cut off to the control chambers 72 and 62 in the device 30 during deenergization of the magnet valve device 432, the additional clearance volume in communication with the cylinder chamber 7 otherwise imposed by these chambers 62 and 72 is eliminated, so that, according to the particular fetaure of the invention provided by the apparatus illustrated in Fig. 5, the com pressor '1 will operate at higher volumetric efficiency at the lower or idling speed of the compressor than during the time when said chambers 72 and 62 are open to said cylinder chamber 7.

Conversely, upon energization of the magnet valve device 432 automatically with increase in speed of the compressor 1 above idling speed, communication of the control chambers 62 and 72 in the valve device 30 with the atmosphere by way of the communication 160 established in magnet valve device 432 when deenergized is interrupted by disestablishment of said communication and said chambers become connected to the cylinder chamber 7 in the compressor 1 by way of communication 161 in the energized magnet valve device, thereby to efiect operation of the device 30 for admission of cooled compressed air to the cylinder chamber 7 in the compressor 1 upon each successive compression stroke of the piston 5, as will be appreciated from previous description in awasso 1E regard to operation as described in connection with Fig. l, for example.

During operation of the apparatus as illustrated in Fig. 5', it will be appreciated that, when the control chambers 62 and 72 in the device 30 are vented to the atmosphere by way of the communication 160 in the deenergized magnet valve device 432, during each successive inlet stroke of the compressor piston 5, atmospheric air will be admitted to the cylinder chamber 7 by way of the suction strainer device 50, the pipe 51, the chamber 53, the ports 54 in the partition 52, the chamber 41 and port 43, the pipe 48, and, in the compressor device, the port 12, inlet chamber 13, bore 14, and the inlet valve 9 successively unseated by the suction etfect produced by piston movement.

An alternate arrangement for interlocking operation of the device30 with speed of the compressor 1 is provided by the apparatus illustrated in Fig. 6. Such apparatus comprises the same components as is comprised in the apparatus illustrated in Fig. 5. According to the alternate arrangement, however, the chamber 137 of magnet valve device 432 is connected to the control chamber 72 in the device 30 by way of pipe 81, the chamber 138 in the magnet valve device 132 is connected to the choke and check valve device 31 via a pipe 300, and the chamber 136 is connected to a branch of the pipe 47. The opposite terminals 152, 153 of the magnet valve device 432 are connected to the wires 220 and 203 in a manner identical to that in which they are so connected in the apparatus illustrated in Fig. 5, so that the magnet valve device 432 in Fig. 6 will be deenergized at or below idling speeds of the compressor 1, and energized at speeds above idling speeds.

In operation of the apparatus illustrated in Fig. 6, when the magnet valve device 432 is deenergized at or below idling speed of the compressor 1, the control chamber 72 in device 30 will be opened to the respective branch of the pipe 47 by way of the communication 160 in the magnet valve device, so that such chamber 72 will be charged with fluid at reservoir pressure and will maintain the piston 70 in device 30 in its lowermost position, opposite to that in which it is shown in Figs. 1 and 2 in the drawing, holding the piston valves 37 and 38 and the piston 58 in their lowermost positions, in which they are shown in said Figs. 1 and2, for maintaining establishment of communication between the compressor inlet chamber 13 and the suction strainer device 50 by way of, in device 30, the chamber 53, ports 54, chamber 41, and port 43, and the pipe 48, while maintaining disestablishment of communication between the pipe 48, and thereby inlet chamber 13 in the compressor 1, and the cooling air supply pipe 46 by way of the chamber 40 in said device 30.

Upon energization of the magnet valve device 432 of the arrangement shown in Fig. 6 with increase in speed of operation of the compressor 1 above idling speed, the pipe 81 and thereby the chamber 72 in the device 30 will be disconnected from the respective branch of the pipe 47 by disestablishment of communication 160 in the magnet valve device 432 and said pipe 81 will become connected to the pipe 300 by way of communication 161 in said magnet valve device, whereby both chambers 62 and 72 in device 30 are then connected to cylinder chamber 7 in compressor 1, so that the device 30 will operate to effect admission of cooled compressed air to the cylinder chamber 7 in the compressor 1 upon each successive compression stroke of said compressor in the manner as previously described in connection with operation of the apparatus illustrated in Fig. 1 for example.

Having now described my invention, what I claim as new and desired to secure by Letters Patent, is

1. In combination with a source of compressed air from which the heat of compression has been removed, a reciprocating piston type air compressor having a cylinder chamber for compression of air and an inlet commu- 1'4 nication'for admittance of air thereto, and means controlled by the pressure of the air obtaining in said cylinder chamber to connect said inlet communication selectively to the atmosphere and to said source during each successive inlet stroke and compression stroke, respectively, of said compressor.

2. In combination with a reservoir for storing compressed air, a reciprocating piston type air compressor adapted'to receive inlet air into a cylinder chamber for compression and delivery to said reservoir, cooling-airadmittance control means controlled by the air pressure obtaining in said cylinder chamber for effecting admit-- tance of compressed air from said reservoir to said cylinder chamber for mixture with said inlet air while in the process of being compressed, means responsive to the air pressure obtaining in said reservoir to render said cooling-air-admittance control means inettective to admit compressed air into said cylinder chamber when air pressure in said reservoir is below a certain value, and cooling means external to said compressor for removing the heat of compression from the compressed air prior to admission into said cylinder chamber.

' 3. The combination with a fluid pressure storage reservoir, an air compressor having a cylinder chamber, air inlet means including a check valve for establishing a one- Way-fioW communication for admittance of air into said cylinder chamber, air outlet means including a check valve for establishing a one-way-flow communication for discharge of air from said cylinder chamber to said reservoir, and a piston movable in said cylinder chamber alternately through successive inlet strokes to draw air into said cylinder chamber via said air inlet means and successive compression strokes to compress and discharge via said air outlet means the air in said cylinder chamber admitted via said inlet means; air admission control means controlled by the pressure of air obtaining in said cylinder chamber to connect said air inlet means to the atmosphere during each inlet stroke of said'piston toenable admittance of atmospheric air into said cylinder chamber for compression and to connect said air inlet means to said reservoir for a period during each compression stroke of said piston to cause compressed air therefrom to be admitted to said cylinder chamber for cooling purposes;.

and means, external of said compressor, for cooling the compressed air admitted via said inlet means to said cylinder chamber while such compressed air is enroute from said outlet means to said inlet means via said reservoir and said admittance control means.

4. The combination as set forth in claim 3, including means responsive to the pressure of the air in said reservoir to prevent said admission control means from connecting said air inlet means to said reservoir when the pressure of fluid in said'reservoir is less than a predetermined value below which cooling of the compressor is undesired.

5. In combination with an'air storage reservoir and a reciprocating type air compressor having a compressor cylinder chamber in which air is compressed for delivery to said reservoir and having compressor-air-inlet means allowing for one-way-fiow'admittance of air into said cylinder chamber; a compressor-air admittance control device comprising valve means movable to an inlet-airadmittance position for connecting said compressor-airinlet means to the atmosphere and movable to a coolingair-admittance position for connecting said compressorair-inlet means to said source of compressed air, first piston means operative responsively to pressurization of a first control chamber above a certain first value to efiect movement of said valve means to its cooling-air-admittance position, second piston means operative responsively to pressurization or" a second control chamber above a certain second value, higher than said first value, to move said valve means to its inlet-air-admittance position, and biasmeans for returning said second piston means to an inoperative position responsively to efiective depressurization of said second control chamber; choke-and-check valve means having a choke-and-check valve inlet for connection with said compressor cylinder chamber and a choke-'and-check valve outlet for connection with said second control chamber, said choke-andcheck valve means permitting facile flow of air under pressure from its inlet to its outlet and restriction of flow of such air in the opposite direction; and cooling means for removing heat of compression from compressed air admitted into said compressor.

6. The combination set forth in claim 5, including conduit means constantly connecting said choke-and-check valve inlet and said first control chamber to said compressor cylinder chamber, and constantly connecting said second control chamber to said choke-and-check valve outlet; a

7. The combination set forth in claim 5, including conduit means constantly connecting said second control chamber to said choke-and-check valve outlet, means to connect said choke-and-check valve inlet and said first control chamber to said cylinder chamber responsively to pressure of air in said reservoir below a certain first pressure and to connect said choke-and-check valve inlet and said first control chamber to the atmosphere and to said reservoir, respectively, responsively to pressure of air in .said reservoir above a certain second pressure, higher than said first pressure.

8. The combination set forth in claim 5, including shuttle valve means having an outlet constantly connected to said first control chamber and also having one shuttle valve inlet and a second shuttle valve inlet, a first conduit constantly connecting said one shuttle valve inlet to the said choke-and-check valve inlet, a second conduit constantly connectingsaid second control chamber to said choke-and-check valve outlet, a magnet valve device energizable and deenergizable to connect said first conduit selectively to said compressor cylinder chamber and to the atmosphere, respectively, a valve device responsive to pressurization of air in said reservoir above a certain one pressure to connect said second shuttle valve inlet to said reservoir and responsive to pressurization of air in said reservoir below a certain other pressure, less than said certain one pressure, to connect said second shuttle valve inlet to the atmosphere, and means responsive to pressurization and depressurization of said second shuttle valve inlet to deenergize and energize, respectively, said magnet valve device.

9. The combination as set forth in claim 5, including a first magnet valve device energizable and deenergizable to connect said first control chamber selectively to .said choke-and-check valve inlet andto said reservoir, respectively,a second magnet valve device energizable and deenergizable simultaneously with said first magnet valve device to connect said choke-and-check valve inlet selectively to. said compressor cylinder chamber and to the atmosphere, respectively, conduit means constantly con-' said' compressor cylinder chamber and deenergizable to connect said choke-and-check valve inlet and said first control chamber to the atmosphere, conduit means constantly connecting said second control chamber to said choke-and-check valve outlet, and means to effect energizationand deenergization of said magnet valve device responsively to speed of operation of said compressor above and below, respectively, a certain speed.

11. The combination as set forth in claim 5, including a conduit constantly connecting the said choke-and-check valve inlet and said first control chamber to said compressor cylinder chamber, a magnet valve device energizable to connect said second control chamber to said choke-and-check valve outlet and deenergizable to connect said second control chamber to said reservoir, and means to effect energization and deenergization of said magnet valve device responsively to speed of operation of said compressor above and below, respectively, a certain speed.

References Cited in the file of this patent UNITED STATES PATENTS 1,611,866 Aikman Dec. 28, 1926 1,893,171 Kagi Jan. 3, 1933 1,967,935 Herzmark July 24, 1934 FOREIGN PATENTS 96,726 Switzerland Nov. 1, 1922 

